A house in sheep's clothing

Just under half of CO2 emissions in the UK come from the energy used in the nation’s buildings. Furthermore, as our houses are often three times less efficient than, for example, German homes, the average house currently loses a quarter of the heat generated to warm it through its roof. Although 72 per cent of all houses in Great Britain do have some loft insulation, most would benefit from more. If every house in the UK installed up to 250 millimetres (10 inches) of insulation, the equivalent financial savings would pay the energy bills of 600,000 families for a year. The only catch is that most insulation is made from artificial, and often highly toxic, materials.

One of the best natural alternatives is wool. But when Christine Armstrong set out to use wool to renovate her 17th-century Cumbrian farmhouse, she found that, despite the abundance of sheep in Cumbria, she would have to import the wool from overseas; the coarse wool from nearby Cumbrian highland sheep was simply going to waste. This led her and business partner David Baldry to set up Second Nature and create Thermafleece, an insulation material made entirely of British wool. Not only does Thermafleece reduce damp and ‘sick building syndrome’, it also provides a lifeline for Cumbrian sheep farmers, devastated by both foot and mouth, and the collapse of the Russian sheepskin market.

How Thermafleece works

Thermafleece has many properties that are unique among insulants. Because of its ability to rapidly absorb and release water vapour, Thermal fleece wool insulation can help to keep buildings cool in summer and warm in winter. When the outside temperature increases and begins to heat the wool, it releases moisture; that has a cooling effect on the fibre which reduces the flow of heat to the inside of the building. This can reduce peak temperature by up to 7° centigrade more than alternative forms of insulation. In winter, the absorption of moisture by wool insulation can increase peak temperature by up to 4°c centigrade more than alternative forms of insulation.

Thermafleece’s manufacturing process consumes minimal energy. Thermafleece uses only 14 per cent of the embodied energy that is used to manufacture glass-fibre insulation, therefore paying back its manufacturing energy cost seven times faster than glass fibre.

It can be installed without gloves or protective clothing. It is not irritating to the skin, eyes or respiratory tract and causes no discomfort to site workers during installation. Any fibres which happen to reach the living space will present no hazard to health. Insect proofing and fibre resistance are achieved by the inclusion of naturally derived additives.

The fibre adapts to the shape of rafters, joists and studs to provide a permanently tight fit. Properly installed, Thermafleece will retain its low density and thermal performance – with a life expectancy similar to that of the construction in which it is installed.

Thermafleece is lightweight and easy to handle and install. The material can be easily cut to shape and size with a sharp knife.

It causes no irritation to the skin, eyes or respiratory tract. When installing the product in confined areas a dust mask is recommended to prevent inhalation of existing dust.

Wool has a higher fibre resistance than cellulose and cellular plastic insulants; it does not burn but rather melts away from an ignition source and extinguishes itself.

At the end of its useful life, Thermafleece can be recycled for other environmentally friendly applications. It also contains no permethrin, pyrethroids, pesticides or formaldehydes.

Where you can buy Thermafleece

For more information got to the Second Nature website at www.secondatureuk.com, or call 01768 486285. The company also offers discounts to community groups and charities.

This article first appeared in the Ecologist September 2005

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